True and apparent graft

When a grafting reaction of a monomer Y is carried out onto a polymer X, and the product is thoroughly extracted with a solvent for the polymer Y, the residue is conventionally called a graft; the weight increase in percent of the polymer X due to the unextractable polymer Y is regarded to be percent graft. However, it is possible that a part of polymer Y which is formed in the matrix of polymer X is unextractable only due to entanglement with polymer X. When we determine the amount of polymer Y which is insolubilized by the entanglement, we know the true value of the percent graft. The grafting of methyl methacrylate (MMA) was carried out onto dry or water‐swollen films of poly(vinyl alcohol) (PVA) in the presence of methanol mainly by mutual irradiation technique and the true and an apparent percent graft were compared. It was found that the difference between an apparent percent graft (A) and the true one (B) was considerably large, the fraction of true graft (B/A) ranging from 0.02 to 0.57. The true percent graft and the branch length were also discussed in dependence on the methanol content of the monomer mixture and the degree of swelling of water‐swollen film.